I’ve read several posts that userdefined textmacros (~/Library/Application Support/Developer/Shared/Specifications) were not detected by xcode.
Here is what I’ve found out.
copy the file from /Applications/Xcode.app/Contents/PlugIns/TextMacros.xctxtmacro to the above mentioned directory and add your own macros at the end of the file.
Good luck Bernd
P.S. I even tried to delete all macros except the first part defining with the identifier = objc; but all macros except my own disappeared.